The present invention relates to a cassette for storing an information recording medium, and more particularly to a cassette comprising a casing for holding therein an information recording medium such as a stimulable phosphor sheet or the like in a light-shielding fashion and a cover openably and closably hinged to the casing, the cassette being arranged to deliver the information recording medium easily into a transport system when the cover is opened in an image reading device.
There has recently been developed and widely used, particularly in the medical field, a radiation image recording and reproducing system for producing the radiation-transmitted image of an object using a stimulable phosphor material capable of emitting light upon exposure to stimulating rays. When a certain phosphor is exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays, or ultraviolet rays, the phosphor stores a part of the energy of the radiation. When the phosphor exposed to the radiation is subsequently exposed to stimulating rays such as visible light, the phosphor emits light in proportion to the stored energy of the radiation. The phosphor exhibiting such a property is referred to as a "stimulable phosphor".
In the radiation image recording and reproducing system employing such a stimulable phosphor, the radiation image information of an object such as a human body is stored in a sheet having a layer of stimulable phosphor, and then the stimulable phosphor sheet is scanned with stimulating rays such as a laser beam to cause the stimulable phosphor sheet to emit light representative of the radiation image. The emitted light is then photoelectrically detected to produce an image information signal that is electrically processed for generating image information which is recorded as a visible image on a recording medium such as a photosensitive material or displayed as a visible image on a CRT or the like.
The radiation image recording and reproducing system includes an image reading device for reading the radiation image recorded on a stimulable phosphor sheet. The image reading device reads the radiation image as follows:
The stimulable phosphor sheet is two-dimensionally scanned by a light beam such as a laser beam, and light emitted from the stimuable phosphor sheet in response to application of the light beam is detected in time series by a light detector such as a photomultiplier or the like, for thereby obtaining image information. The two-dimensional scanning of the stimulable phosphor sheet with the light beam is effected by mechanially feeding the stimulable phosphor sheet in one direction for auxiliary scanning, while deflecting the light beam for main scanning in a direction normal to the direction in which the stimulable phosphor sheet is fed.
For recording an image on a stimulable phoshpor sheet in an image recording device, an object to be imaged is exposed to radiation, and the stimulable phosphor sheet stored in a cassette is then exposed to the radiation having passed through the object for recording the radiation image on the stimulable phosphor sheet. The stimulable phosphor sheet as it is carried in the cassette is then loaded into the image reading device, in which the stimulable phosphor sheet is taken out of the cassette by a sheet feed mechanism including a suction cup and delivered to a position where the sheet is scanned by the light beam.
The sheet feed mechanism includes a vacuum generator for enabling the suction cup to attract and take a stimulable phosphor sheet out of the cassette. For reliable delivery of the stimulable phosphor sheet from the cassette, the suction cup should be displaced along a desired path by means of links or the like. Therefore, the sheet feed mechanism is complex in structure, large in size, and costly to manufacture. Since the image reading device must be equipped with such a sheet feed mechanism, the image reading device is also large in size and its cost of manufacture is high.
There is also known a system in which the radiation image of an object is recorded on a conventional X-ray film. The X-ray film to which the desired radiation image has been exposed is also stored in a cassette which is then loaded into an automatic developing device or the like. In the automatic developing device, the X-ray film is subsequently taken out of the cassette. The X-ray film cassette causes the same problems as those described above with respect to the cassette for storing stimulable phosphor sheets.